The present invention relates generally to the field of frame members, and more particularly to the field of frame assemblies that are covered with a cover sheet.
Construction assemblies of the type that include frame assemblies that are covered with a cover sheet are well known and function, for example, as awnings, signs, partitions, and various enclosures. The frame assemblies are constructed of a plurality of frame members. One such type of frame members are elongated and define elongated stapling channels. The cover sheet is often constructed from pieces of fabric composed of woven acrylic or vinyl laminated on a polyester scrim. The cover sheet spans between and is stapled or clipped into the stapling channels of the frame members. Once the cover sheet is stapled into a stapling channel, it is common for an elongated bead or strip to be driven partially into the stapling channel. Representative construction assemblies and frame members are disclosed in U.S. Pat. No. 4,926,605 issued to Milliken et al., as well as numerous other patents.
Frame members are often unitary extrusions of aluminum. Aluminum is a relatively soft metal such that steel staples are capable of being readily stapled into the stapling channels of aluminum frame members. Frame members are also often constructed of steel. However, there are some drawbacks to utilizing steel frame members of the type having conventional stapling channels. For example, steel is a relatively hard metal such that it can be impossible to staple steel stapes into the stapling channels of steel frame members. Any such difficulty in stapling will detrimentally increase the costs associated with the use of steel frame members.
The difficulty of stapling into the stapling channel of steel frame members has, to a limited degree, been addressed. As disclosed in U.S. Pat. No. 4,926,605, it is known to place a strip of nylon or similar material at the bottom of a steel stapling channel such that the strip of nylon is capable of readily receiving staples. While the employment of such a strip of nylon does seek to simplify the process of stapling into the stapling channel of steel frame members, it is otherwise of limited value. For example, such a strip of nylon might tend to become dislodged and does not add any substantial strength to the frame member associated therewith. Further, strips of nylon typically have a characteristic of being somewhat "slick" (e.g., they are not abrasive) such that they are ineffective at retaining staples when the cover sheet is subjected to maximum wind and snow loads. Under such conditions the staples have a tendency to pull out of the nylon strip. The inability of the nylon strips to retain staples is enhanced by the fact that the bottom of the stapling channel of a steel frame member is defined by a steel part upon which a nylon strip rests, whereby staples are precluded from substantially passing through the nylon strip. Further, when steel frame members which include nylon strips are welded, the nylon strips tend to burn or melt such that noxious fumes are emitted. Thus, such steel frame members are often joined with mechanical fittings such as tees or elbows, which are cost prohibitive when compared to welded joints. Additionally, mechanical fittings are less versatile in terms of the configurations in which they can be utilized in connecting frame members. That is, a different style of fitting is needed for different joint scenarios. Also, mechanical fittings typically do not provide joints that are as strong as welded joints.
While aluminum frame members that have stapling channels offer benefits greater than steel frame members having stapling channels (with or without nylon stapling strips), there are numerous short comings to such aluminum frame members. In order for staples to be driven into aluminum stapling channels, aluminum must be of a relatively soft temper; typically a T-5. This material has roughly half the strength characteristics of cold formed steel; a relatively weak form of steel. Also, aluminum is a relatively expensive metal when compared to steel, having a cost approximately twice that of cold formed steel. Due to the combination of the relative weakness and higher unit cost of aluminum, aluminum frame members with aluminum stapling channels are considerably more expensive to produce than their steel counterparts. Further, methods used in welding aluminum are more time consuming and technical in nature than those for welding steel, adding additional expense to construction assemblies that include aluminum frame members. Another potential drawback to the employment of aluminum frame members with stapling channels has to do with the number of times that such frame members are capable of being recovered (recovering being the process of removing a cover sheet from a frame assembly and applying a new cover sheet to that same frame assembly). The number of recoverings is potentially limited because there is a limit to the number of times staples can be driven into and removed from the stapling channel of an aluminum frame member. If staples are repeatedly applied to and removed from the stapling channel, the pan that defines the bottom of the stapling channel will eventually become so perforated that it will not effectively retain staples. This limits the number of times that a given frame assembly is capable of being readily recovered.
There is, therefore, a need in the industry for a method and an apparatus which solve these and other related, and unrelated, problems.